1. Technical Field
The present invention relates to a method for producing an actuator device having on a vibration plate a piezoelectric element composed of a lower electrode, a piezoelectric layer consisting of a piezoelectric material, and an upper electrode; the actuator device; and a liquid-jet head and a liquid-jet apparatus using the actuator device.
2. Related Art
An example of a piezoelectric element for use in an actuator device is a combination of a piezoelectric layer comprising a piezoelectric material showing an electromechanical transducer function, for example, a crystallized piezoelectric ceramic, and two electrodes, i.e., a lower electrode and an upper electrode, sandwiching the piezoelectric layer. Such an actuator device is generally called an actuator device in the flexural vibration mode, and is used, for example, in a liquid-jet head. A representative example of the liquid-jet head is an ink-jet recording head in which a part of a pressure generating chamber communicating with a nozzle orifice for ejection of ink droplets is composed of a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize ink in the pressure generating chamber, thereby ejecting ink droplets through the nozzle orifice. An example of the actuator device installed in the ink-jet recording head has a piezoelectric element formed by forming a uniform piezoelectric material layer on the entire surface of the vibration plate by film lamination technology, and cutting the piezoelectric material layer into shapes corresponding to the pressure generating chambers by lithography to form the piezoelectric element for each of the pressure generating chambers (see, for example, JP-A-5-286131 (FIG. 3, paragraph [0013])).
The actuator device having such a piezoelectric element is advantageous in that the piezoelectric elements can be fabricated with high density by lithography, which is a precise and convenient method, and that the piezoelectric element can be thinned, enabling high speed driving. However, the problems arise that the piezoelectric element formed in this manner undergoes film peeling or delamination due to the film quality or film stress of each film constituting the piezoelectric element. In particular, the upper electrode, which is the uppermost layer of the piezoelectric element, is apt to peel off the piezoelectric layer.
To adjust the stress of the film constituting the piezoelectric element, a stress relaxation layer may be provided between the piezoelectric layer and the opposed film (for example, JP-A-2004-128492 (Claims)). Such a configuration can be expected to prevent, to some degree, the delamination of the film constituting the piezoelectric element. However, the problem is likely to occur that the piezoelectric characteristics of the piezoelectric layer decline, failing to obtain the desired amount of displacement when the piezoelectric element is driven.
Of course, such problems exist not only in the actuator device installed in the liquid-jet head such as an ink-jet recording head, but similarly in the actuator device installed in every other apparatus.